1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method for transmitting reference signals in a wireless communication system based on Time Division Duplex (TDD) and an apparatus using the same.
2. Related Art
Long Term Evolution (LTE) based on 3rd Generation Partnership Project (3GPP) Technical Specification (TS) release 8 is a strong next-generation mobile communication standard. Recently, the standardization of LTE-Advanced (LTE-A) based on 3GPP TS release 10 which supports multiple carriers is in progress.
As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, reference signals, such as a Cell-specific Reference Signal (CRS), a Primary Synchronization Signal (PSS), and a Secondary Synchronization Signal (SSS), and control channels, such as a physical downlink control channel (PDCCH) and a physical broadcast channel (PBCH), are defined in the physical layer of 3GPP LTE/LTE-A.
3GPP LTE supports both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). In FDD, uplink (UL) transmission and downlink (DL) reception are performed in different frequencies. In TDD, uplink (UL) transmission and downlink (DL) reception are performed in the same frequency. A terminal supporting full-duplex FDD is capable of simultaneous UL transmission and DL reception at a specific time. A terminal supporting half-duplex FDD and TDD is incapable of simultaneous UL transmission and DL reception.
Meanwhile, in LTE releases 8/9/10, reference signals and control channels are transmitted in all the DL subframes. In the next-generation system, however, in order to more efficiently use radio resources, it is expected that a new type of a carrier in which some or all of reference signals and control channels are not transmitted will be introduced. Such a carrier type is called a New Carrier Type (NCT).